The present invention relates generally to pens utilizing fibrous nibs to wick ink onto a surface to be marked. More particularly, the invention relates to such a pen utilizing an improved fibrous nib constructed of synthetic fibers, as well as methods for producing such a nib.
Many different varieties of small marker pens are in widespread use, both in business and in the home. While these pens may occasionally utilize a nib constructed of plastic or foam, fibrous nibs are often preferred. As is well known, these nibs function to supply ink from an ink reservoir within the pen.
A number of different fibrous nibs have been developed in the past for use in small marker pens. Although often referred to as "felt" tips, these nibs are actually constructed of a variety of materials and by a variety of different methods. The specific type of nib utilized in a given application will often depend upon a number of factors, such as wick performance for a particular ink, and cost.
Generally, fibrous nibs of this type fall into three broad classes: (1) sculptured nibs constructed of wool felt; (2) die cut nibs constructed of needled polyester; and (3) sculptured nibs constructed of longitudinal fibered polyester.
(1) Wool Felt Nibs
Wool felt nibs are often characterized by a relatively high density, exhibiting a specific gravity of 0.325 or higher. Due to this relatively high density, wool felt nibs may be easily ground or cut into various shapes. For example, these nibs are often ground into a shape having a cylindrical body portion with a conical end portion tapering to a tip.
The process of making a wool felt nib begins with the production of felt. To produce the felt, a blend of wool fibers, which are generally size 64 or finer, is first carded. After carding, webs of wool fibers are generally laid upon each other to produce a batt. This combined batt constitutes felt, which is generally of the type identified by the trade style designation S-1.
The combined batt may then be hardened under a large heated platen. The platen is often attached to four columns which oscillate in an orbital pattern. This process compresses the batt, thereby hardening it as desired.
The hardened batt may then be fulled to the desired density. Fulling is a process of increasing the weight and bulk of the batt, typically by beating it in a kicker mill, or running it through a series of offset rollers. Typically, a five percent sulfuric acid solution is used as a fulling agent, along with heat and steam.
After fulling, the batt may be dried and subjected to a process referred to as "B-staging." B-staging involves first saturating the felt with a solution containing a thermoset resin, typically a melamine resin. After saturation, the resin is cured to produce relatively stiff sheets of the felt. These sheets may be pressed to control thickness, as well as to stabilize the wool against swelling when brought into contact with ink. The sheets may then be subjected to stripping, after which nibs having the desired configuration may be produced.
In part because of the relative ease with which wool felt nibs may be sculptured into various shapes, they are seen as very desirable. However, nibs produced from wool have had a tendency to be somewhat costly. Additionally, recent environmental regulations have imposed obligations which have made the process of producing wool felt nibs more difficult. These environmental regulations mandate that the sulfuric acid used as a fulling agent, as well as various lanolins and oils extracted from the wool during processing, must be disposed of in a designated manner.
Thus, despite their advantages, the use of marker pens having wool felt nibs has generally been limited to certain specialized applications in which cost is not the primary consideration. One such application is the marking of cardboard containers in an industrial shipping and receiving facility. Additionally, while wool felt nibs work well with solvent-based inks, they are not as effective in wicking water-based inks.
(2) Die-Cut Polyester Nibs
After the development of wool felt nibs, polyester nibs constructed of a needled nonwoven substrate were developed. Generally, these nibs are less expensive than wool felt nibs and work well with water-based inks. As such, these nibs are often cut into a parallelogram shape and utilized in highlighters and other low cost marker pens.
Prior art polyester nibs have generally been constructed of fibers having a size of three denier to six denier. Generally, the polyester fibers are first carded, after which a batt is produced. The batt may be produced by laying up the carded fibers using a cross lapper with a variable feed apron. The batt's weight per unit of planar area may be controlled by varying the speed of the apron.
Typically, the batt continues on an apron to a set of compression rolls, after which it may be passed between the stripper plates of a needling loom. In the needling loom, the batt is needled from both sides to entangle the polyester fibers, thus creating a nonwoven substrate material.
Next, sheets of the substrate material may be treated with an appropriate resin solution. Typically, the resin solution utilized will be a thermoset resin (such as melamine), but elastomeric resins are not uncommon for this purpose. After being treated with resin, the sheets are pressed in a manner similar to wool felt sheets.
The stiffened polyester sheets produced by this process typically had a specific gravity of approximately 0.22 to 0.28. As can be seen, this is significantly less dense than the stiffened wool sheets utilized to produce wool felt nibs. It has been very difficult to produce sculptured nibs constructed of this lower-density material. Thus, although needled polyester nibs are generally more economical than wool felt nibs, their use has typically been limited to applications in which a sculptured nib is not believed necessary.
(3) Longitudinal Fibered Nibs
Longitudinal fibered nibs were developed to pass high-pigmented inks or other fluids, and can generally be used for either solvent or water-based inks. This type of nib is typically produced utilizing polyester fibers having a size of approximately three (3) to six (6) denier. After appropriate carding, the fibers are longitudinally bundled to meet a total denier specification. In the art, a group of fibers which have been bundled in this manner is often referred to as "tow."
The tow may then be processed in a "pulltruder" device, which can be thought of as having three sections. In the first section, the tow is generally pulled through a cone-shaped heated die. The second section of the pulltruder may contain a bath of resin solution, through which the tow is passed. In the third section, the tow is dried and the resin is B-staged. The third section also generally contains a cone-shaped heated die, which finish cures the resin.
The pulltruder device produces a rigid rod which may be flat or round in cross section. These rods are relatively dense, typically having a specific gravity of greater than 0.36. As a result, the rod may be sculptured into various shapes as desired. However, because the tow is typically drawn from the pulltruder device at a speed of approximately four inches per minute, nibs produced in this manner tend to be very expensive.